The invention concerns a method for controlling a floor heating system, in which, within a cycle, a heating circuit in a room is supplied with a heat carrying fluid for a supply period, the supply period being chosen in dependence of the room temperature.
A method of this kind is known from DE 37 08 449. In the known case, it is endeavoured to avoid an irregular temperature distribution on the floor surface, which could occur in connection with a throttling. The throttling could namely cause the heat carrying fluid to be cooled before leaving the heating circuit. Therefore, the heat carrying fluid is not throttled, but the cycles are controlled, during which the heat carrying fluid can flow through the heating circuit. The cycle durations are specified by the system manufacturer. They are in the range from 26 to 36 minutes. Within each cycle, the user or a room temperature controller can state an OFF-period, which can be in the range from 0 to 24 minutes. The shorter the duration of the OFF-period, the more intensively the room is heated.
This control method is not optimal with regard to the energy consumption.
The invention is based on the task of providing a more favourable operation of a floor heating system with regard to the energy consumption.
With a method as mentioned in the introduction, this task is solved in that next to the room temperature at least one additional parameter is registered, the cycle duration and the duration of the supply period being chosen in dependence of the room temperature and the parameter.
With this method, firstly the number of influence sizes is increased, which are considered in connection with the control. Secondly, however, also the number of intervention opportunities is increased, that is, not only one size, but two sizes, is controlled. Here, various opportunities exist. The cycle duration on a whole can be changed and at the same time, during the cycle, also the supply period can be changed. However, the supply period can also be regarded as ON-time and the remaining period of a cycle as OFF-time, ON-time and OFF-time, respectively, being changed. The relation between these two times is determined in dependence of the load on the heated room. Thus, it is no longer required that fixed cycle durations are observed, which is particularly disadvantageous, when changes occur during a cycle duration, which have a substantial influence on the room temperature. This control method is particularly advantageous when it is desired to keep a room temperature constant.
It is preferred that a thermal time constant for the room is chosen as a parameter. The time constant is a measure for how fast the room is heated when supplied with a certain heat amount. The heat amount supplied is known, or can be calculated from the difference between the supply temperature and the return temperature as well as the supply quantity. By means of the time constant, the ON-time and the OFF-time can now be calculated in such a way that a desired temperature is maintained. During the heating phase of the room or the cooling, respectively, the time constant will be less considered during a large share of this phase, and, for example, perform the heating with the highest possible output.
Preferably, different time constants are used for heating and cooling. Thus, it is possible to keep the room temperature even closer to the desired value.
Preferably, the time constant is determined on the basis of measurings of the room temperature at different Preferably, these times are in a heating phase or a cooling phase, respectively. When, however, the room is maintained at the desired temperature, it is more difficult to determine the time constant. In a manner of speaking, the method is adaptive. When the room temperatures are measured at different times, the time constants can be determined. Above all, this method is advantageous in that the time constant can be corrected continuously or from time to time, to consider changes, which have occurred in the room itself or in its neighbourhood.
Preferably, the system is switched to comfort operation, when for a certain period no heating requirement has existed, the heating circuit being supplied with heat carrying fluid during comfort operation in such a way that the room is not heated. In many cases, typically periods exist, in which heat is not required from the floor heating system. Such a situation may occur, when the room is heated by solar irradiation. Even though the room temperature then corresponds to the temperature pre-selected by the user, the feeling of comfort may be influenced by the fact that the floor is cooled down. This particularly concerns floors, which are tiled or clinkered. When the user has to walk around on such xe2x80x9cstone floorsxe2x80x9d with bare feet or with socks or thin soles, this will give him an uncomfortable feeling. When, however, the system is switched to comfort operation, it is ensured that merely the floor is heated, the room temperature, however, not being influenced, or at least not significantly. This causes that the user does not find the floor cold. As, however, the room is not heated, the conditions are at least substantially optimal with regard to the energy consumption.
Preferably, a floor temperature is calculated on the basis of several other temperatures, and the cycle duration and the duration of the supply period are synchronised with the floor temperature. It is thus established, which temperature the floor must have to ensure that the room is not further heated. For this purpose, other temperatures can be used, which are available. Now, this floor temperature can be specified as a value and the cycle duration and the duration of the supply or the ON-time and the OFF-time can be synchronised with each other in such a way that the desired temperature occurs. Of course, this can also be achieved by means of a control, during which the floor temperature is measured.
It is particularly preferred that the floor temperature is calculated according to the following formula:       T    F    =            T      L        -                            C          W                          C          L                    ⁢              (                              T            V                    -                      T            R                          )            
TF being the floor temperature,
TL being the air temperature,
TV being the supply temperature,
TR being the return temperature,
CW being the density of water and
CL being the density of air.
With this embodiment, a heat balance occurs. This confirms that
(TVxe2x88x92TR)xe2x80xa2CW=(TLxe2x88x92TF)xe2x80xa2CL.
TV, TR und TL are measured. As CW and CL are constants, TF can be calculated. Then, the ON-times and the OFF-times, respectively, are kept so that TF does not exceed the calculated value. In stead, also the relation between the room temperature TL and the supply temperature TV can be taken into consideration.
Preferably, during comfort operation, the supply is turned off to all other rooms being connected with the same heat source. The heat source is considered to be a place in the heating system, which supplies a heat carrying fluid with a substantially constant temperature independently of the load. During comfort operation, the heat carrying medium thus has the optimum supply temperature, that is, temperature reductions caused by the consumption in other rooms do not occur.